Apparatus and method for isolating an intact portion of a service braking circuit from a failed service brake wheel end

ABSTRACT

An apparatus and method for protecting an intact portion of a service brake system from a failed wheel end of a vehicle is provided. A failure in a wheel end is detected by determining an operation state of each of the wheel ends by monitoring parameters including the pressure in a parking brake air supply line. When it is determined that a failed wheel end is present in the service brake system, a service brake isolation valve is switched to a state in which the failed wheel end is isolated from the rest of the brake system. The service brake of the failed wheel end is disabled, while the service brakes of the other wheel ends are enabled for normal operation. The parking brake of the failed wheel end is enabled, while the parking brakes of the other wheel ends are disabled to prevent immobilization of the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the pending U.S. patentapplication Ser. No. 13/654,946 entitled “Apparatus and Method forIsolating an Intact Portion of a Service Braking Circuit from a FailedService Brake Wheel End” filed Oct. 18, 2012, the entire disclosure ofwhich is incorporated fully herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to vehicle braking systems and, inparticular, to an apparatus and method for isolating an intact portionof a service braking circuit from a failed service brake wheel end.Additionally, the present invention isolates a failed parking brake froman intact portion of a parking brake circuit. By isolating the failedservice brakes and parking brakes of a vehicle from the rest of thebraking system, complete immobilization of the vehicle can be preventedwhile maintaining use of the antilock braking system (ABS) in the eventof a wheel end failure.

The present invention protects the intact wheel ends of a servicebraking circuit from a failure of a portion of the failed circuit. Theoperation state of the parking brake of each wheel end may be determinedby monitoring air line pressure, force applied to the wheel end, wheelspeed, temperature at the wheel end, and/or other like parameters. Whena failed wheel end is detected, the remaining intact wheel ends'servicebrake control is protected and isolated from the failed wheel end.

Moreover, it is desirable to maintain use of the ABS in the event of aservice brake failure. With rear axle wheel end failures, for example,braking systems often revert to spring brake modulation, but thiseliminates antilock braking on all wheel ends of the affected brakingcircuit. The present invention, however, allows for ABS control on theintact wheel ends of a braking circuit with a failed wheel end. Further,the present invention allows for more system pressure to be retainedwith the failed wheel end by isolating the failed pneumatic wheel endfrom the intact portion of the pneumatic braking system.

In accordance with an exemplary embodiment of the present invention, anantilock braking system control unit is used to control individualservice-braked wheel ends by using ABS modulators as isolation devices.Many different parameters can be used to sense individual parking brakestatus, such as air line pressure, wheel speed, stroke, torque, wheelslip, temperature and the like. In particular, it is desirable to usepark line pressure to isolate the pressure to the service side of thefailed wheel end.

As an alternative to the above-described electronic control embodiment,a pneumatic control or an electro-pneumatic control can be used tocontrol the braking system. In particular, pneumatic isolation valvescan be used to isolate the service brake side of the system.

With regard to parking brakes, commercial vehicles are typicallyequipped with spring-actuated/fluid released parking brake systems, inparticular pneumatic systems which utilize compressed air to release theparking brake actuator of each wheel end's spring brake actuator. Theparking brakes in such vehicles remain released as long as the parkingbrake release pressure is maintained in spring brake actuators. Suchsystems typically have a common source of pressure connected to eachwheel end's spring brake actuator, such that application of pressure tothe common lines simultaneously releases the vehicle's parking brakes.

A single point of failure in such systems may result in application ofall of the wheel end spring applied parking brake portions of theparking brake actuators, effectively immobilizing the vehicle. Forexample, in a typical 6×4 vehicle, a rupture of any one of the fourpneumatic lines to the wheel ends could result in parking brake releasepressure being bled off from all four spring brake actuators. This hasbeen the standard industry design practice, as a failure of a singlebrake actuator or the pressure delivery to a single axle has been viewedas a serious event warranting automatic full application of all of thevehicle's brakes as desirable “fail safe” outcome.

Notwithstanding the common industry design practice, there may also besituations in which full parking brake application and the resultingcomplete immobilization of the vehicle could have undesiredconsequences. For example, in a commercial application of a vehicle withmultiple axles such as a logging truck, being forced to park orautomatically immobilize the vehicle in the event of a parking brakerelease pressure failure at one wheel end may be highly undesirable whenthe vehicle is at a remote location (such as deep in a forest on alogging road), where repair facilities are far away and/or theimmobilization of the vehicle may block a much-needed passage, such as afire road in the case of a logging truck or the travel lanes of a highspeed, high vehicle volume highway in the case of an over-the-roadcommercial vehicle.

Other examples where automatic application of all spring applied parkingbrakes in the event of a single wheel end failure may be undesirableinclude heavy police vehicles or military vehicles which may besubjected to combat conditions such as criminal attacks or exposure toimprovised explosive devices (“IEDs”). During such an event, damage to apneumatic line serving one wheel end in a prior art common-supplyparking brake system could cause all of the wheel ends' parking brakesto be immediately applied, effectively immobilizing the vehicle in alocation where the vehicle and its personnel would be vulnerable tofurther attacks.

It would be desirable to have a brake system which, in addition topermitting full parking brake release and application capability innormal operating conditions, also responds to a line failure at onewheel end in a manner which provides for continued reliable release andapplication of the parking brakes of the remaining undamaged wheel ends.

The present invention solves the above-described and other problems ofthe prior art by arranging devices at each wheel end which function aswheel end shut-off devices to isolate the damaged wheel end from theremaining portions of the service brake system and the parking brakesystem while not restricting flow during spring brake modulation.

The invention is not limited to damage affecting solely the linesbetween the flow control components and a parking brake actuator, butincludes any damage at a wheel end which may result in the release ofparking brake release pressure, such as damage to the parking brakerelease actuator portion of a wheel end's spring brake actuator.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a portion of a system for isolating aservice brake wheel end failure according to an exemplary embodiment ofthe present invention.

FIG. 2 is a schematic diagram of a portion of a system for isolating aservice brake wheel end failure according to another exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic diagram of a portion of a braking system forisolating a service brake wheel end failure according to an exemplaryembodiment of the present invention in which an antilock braking systemcontrol unit determines the presence of a failed wheel end.

The partial system 100 illustrated in FIG. 1 includes a pair offoundation brakes 2 and 3, which are connected to spring brake actuators4 and 5, respectively, for actuation of the foundation brakes. Only apartial system is illustrated to simplify the illustration and itscorresponding description. The foundation brakes 2 and 3 may be S-cambrakes, air disc brakes or the like. Of course, the system could includemany more foundation brakes, spring brake actuators, and the like.

The spring brake actuators 4 and 5 are composed of separate mechanicaland fluid (e.g., air) actuators in one housing. The fluid appliedportion of the actuator functions as the service brake, while themechanical portion functions as the parking/emergency brake. The serviceactuator requires air pressure to apply the service brakes, while theparking/emergency actuator uses air pressure to release the brakes. Thespring brake actuators 4 and 5 may be, for example, Bendix® Eversure®Spring Brakes available from Bendix Commercial Vehicle Systems LLC ofElyria, Ohio.

As shown in the drawing, each of the foundation brakes 2 and 3 may havea wheel speed sensor 6 and 7, respectively, which is located adjacent tothe brake for monitoring wheel speed. The wheel speed sensors 6 and 7may alternatively, or additionally, be other types of sensors formonitoring a variety of parameters, such as wheel speed, stroke, torque,wheel slip, temperature and the like. As part of the brake assembly, thefoundation brakes 2 and 3 may be provided with automatic slack adjusters8 and 9, which provide torque to rotate the brake camshaft when thebrake pedal is depressed.

A central portion of the system 100 includes an antilock braking systemcontrol unit (ABS-ECU) 10 and a plurality of devices for monitoring andcontrolling the flow of air to/from the spring brake actuators, asfurther described below. The antilock braking system control unit 10 maybe, for example, a Bendix® EC-60™ controller available from BendixCommercial Vehicle Systems LLC.

A service relay 11 is disposed between antilock braking modulators 12and 13. The service relay 11 has a fluid (e.g., air) input (not shown)that provides fluid for the service side of the spring brake actuators 4and 5 and outputs via supply lines 31 and 33 to the antilock brakingmodulators 12 and 13 for actuation of the spring brake actuators 4 and5. The antilock braking modulators 12 and 13 may be, for example,Bendix® M-32™ antilock modulators available from Bendix CommercialVehicle Systems LLC.

On the spring/parking side of the system between the spring brakeactuators 4 and 5, a spring brake control valve 14 is disposed. Thespring brake control valve 14 provides rapid application of the springbrake actuator 4/5 when parking and modulates application of the springbrake actuator 4/5 when a failure occurs in the service brake system.The spring brake control valve 14 may be, for example, a Bendix® SR-7®Spring Brake Modulating Valve available from Bendix Commercial VehicleSystems LLC.

The spring brake control valve 14 has a fluid input (not shown) at thesupply inlet port S. Outputs of the spring brake control valve 14 areprovided to the spring brake actuators 4 and 5 via the differentialprotection valves 15 and 16, pressure indication devices, which may bepressure sensors or pressure switches, 17 and 18, and the supply lines32 and 34 to control the supply of air to the spring brake actuators 4and 5.

The antilock braking system control unit 10 monitors the pressureindication devices 17 and 18 to determine when a wheel end failure hasoccurred. The pressure in the supply lines 32 and 34, for example, maybe monitored to determine when the supply line pressure has droppedbelow a threshold value that indicates a failure in the wheel end. Inother words, when the normal parking brake line pressure has been lost,there is a failure at the wheel end.

When the pressure in a parking brake supply line 32/34 indicates a wheelend failure, the normally operating spring brake actuator 4/5 isisolated so that the failed wheel end does not negatively impact thewhole braking system in a manner that immobilizes the vehicle ordeactivates the functioning of the intact wheel ends. To isolate theintact system from the failed portion of the system, the antilockbraking system control unit 10 closes the antilock braking modulator12/13 at the failed wheel end only. Accordingly, the antilock brakingsystem control unit 10 maintains control of the ABS for the intactportion of the braking system. That is, the wheel ends that do not havea failure are able to maintain proper functioning of the service brakingsystem including the ABS. By contrast, the service brake at the failedwheel end is shut off.

Additionally, when a failure at a wheel end is determined, although theparking brake at the failed wheel end is enabled, the other parkingbrakes are protected and will not actuate automatically since the air ismaintained in the parking release portion of the spring brake actuator,which prevents immobilization of the vehicle. In particular, when adifferential protection valve 15/16 determines that pressure has beenlost in a supply line 32/34, the differential protection valve 15/16closes to prevent flow of fluid to the failed wheel end. Without theflow of fluid, the parking brake of the failed wheel end cannot bedisabled, and thus remains enabled.

FIG. 2 is a schematic diagram of a portion of a system for isolating aservice brake wheel end failure according to another exemplaryembodiment of the present invention in which service brake isolationvalves isolate a failed wheel end from the rest of the service brakingsystem. Some of the elements of FIG. 2 are the same as those in FIG. 1.Accordingly, the description of those elements is not repeated here.Unlike partial system 100 of FIG. 1, partial system 200 illustrated inFIG. 2 does not have an antilock braking system control unit.

The embodiment illustrated in FIG. 2 provides a pneumatic isolationvalve 21/22 for each of the wheel ends. The service brake isolationvalves 21 and 22 are connected between the antilock braking modulator12/13 and the spring brake actuator 4/5 for each of the wheel ends fordetermining an operation state of each of the wheel ends and controllingantilock braking of each of the wheel ends, individually, based upon theoperation state.

In particular, pressure indication devices 23 and 24 determine when thesupply lines 32 and 34 have a pressure below a threshold value whichindicates a fault condition in the parking brake line pressure. Theoutputs of the pressure indication devices 23 and 24 are provided to thecontrol port C of the service brake isolation valves 21 and 22,respectively. Accordingly, when the service brake isolation valve 21/22receives a control input from the pressure indication device 23/24indicating that the park line pressure is too low, the service brakeisolation valve 21/22 shuts off, which isolates the failed wheel end.

Like the embodiment described above in relation to FIG. 1, theembodiment of FIG. 2 also provides for protecting the parking brakes atthe wheel ends that do not have a failure, while the parking brake of afailed wheel end is enabled. Thus, the failed wheel end is isolated fromthe rest of the braking system.

The present invention's isolation capability may be omitted onindividual wheel ends, for example, at wheel ends judged to not bevulnerable to parking brake release pressure disruption, or where costsare to be minimized by only providing isolation capability for a subsetof a vehicle's wheel ends.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. For example, rather thanproviding flow control arrangement dedicated to a single wheel end, asingle flow control arrangement may serve both wheel ends of an axle ofthe vehicle, such that in the event of damage to the lines of that axle,the service brakes and ABS of the remaining axle(s) may remainoperational and the parking brake release actuators of the remainingaxle(s) may be maintained in the released position so that the vehiclemay be moved if the other axles can overcome the resistance of thewheels of the damaged axle. Because other such modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. An apparatus for protecting an intact wheel endof a brake system from a failed wheel end, comprising: A first springbrake actuator having a service brake portion and a parking brakeportion and associated with a first wheel end; A second spring brakeactuator having a service brake portion and a parking brake portion andassociated with a second wheel end; a first and second differentialprotection valve communicating with the spring brake control valve andthe respective first and second spring brake actuators for controlling asupply of fluid for releasing the parking portions of the first andsecond spring brake actuators; and a first and second service brakeisolation valve communicating with the first and second differentialprotection valves and the respective first and second spring brakeactuators for determining an operation state of the first and secondwheel ends, wherein, based upon a failed operation state of the firstwheel end, the first service brake isolation valve isolates the failedfirst wheel end and prevents the parking brake portion of the secondspring brake actuator that is in a normal operation state fromautomatically applying.
 2. The apparatus of claim 1, wherein theoperation state is determined based upon a pressure in a fluid supplyline to the first and second spring brake actuators.
 3. The apparatus ofclaim 1, wherein the fluid is a gas.
 4. The apparatus of claim 1,wherein, in response to a failed operation state of the first wheel end,the first service brake isolation valve closes delivery to the firstspring brake actuator.
 5. The apparatus of claim 1, wherein theoperation state of the first wheel end is determined based upon at leastone of a pressure in a fluid supply line to the parking brake portion ofthe first spring brake actuator, an applied force at the first springbrake actuator, a wheel speed, a temperature of the friction interface,and a wheel slip.
 6. An apparatus for protecting an intact portion of aservice brake system of a vehicle having at least two wheel ends from afailed wheel end, comprising: a spring brake actuator provided for eachof the wheel ends for actuating a service brake and releasing a parkingbrake; a spring brake control valve for controlling actuation of thespring brake actuator for parking braking; a differential protectionvalve provided for each of the wheel ends for controlling a first supplyof fluid to the spring brake actuator for releasing the parking brake; arelay valve for applying and releasing the service brake via the springbrake actuator; and a service brake isolation valve provided for each ofthe wheel ends for determining an operation state of each of the wheelends and protecting the intact portion of the wheel ends individually,based upon the operation state.
 7. The apparatus of claim 6, wherein theoperation state of each of the wheel ends is determined based upon apressure in a fluid supply line to the spring applied parking brake. 8.The apparatus of claim 6, wherein the fluid is a gas.
 9. The apparatusof claim 6, wherein, when the operation state of a first wheel end ofthe at least two wheel ends is a fault state, the service brakeisolation valve closes delivery to the first wheel end, while theservice brake isolation valve of the at least two wheel ends that are ina normal operation state keeps open the delivery to the wheel ends thatare in the normal operation state.
 10. The apparatus of claim 6, whereinthe operation state of each of the wheel ends is determined based uponat least one of a pressure in a fluid supply line to the parking brake,an applied force at the spring brake actuator, a wheel speed, atemperature of the friction interface, and a wheel slip.
 11. Theapparatus of claim 6, wherein, when the operation state of a first wheelend of the at least two wheel ends is a fault state, the differentialprotection valve protects the parking brake of each wheel end of the atleast two wheel ends that is in a normal operation state.
 12. Anapparatus for protecting an intact wheel end of a brake system from afailed wheel end, comprising A spring brake actuator associated witheach of at least two wheel ends having a service brake portion and aparking brake portion; a spring brake control valve for controllingactuation of the parking portion of a respective spring brake actuator;means for controlling a supply of fluid for releasing the parkingportion of the spring brake actuators; and a first and second servicebrake isolation valve communicating with the means for controlling asupply of fluid and a respective spring brake actuator for determiningan operation state of each of the at least two wheel ends, wherein,based upon a failure of a first of the at least two wheel ends, themeans for controlling a supply of fluid prevents the parking brake ofthe of each wheel end of the at least two wheel ends that is in a normaloperation state from automatically applying.